Preheat the oven to 375°F.
In an oval baking dish, toss together the tomatoes, peppers, olives, 2 tablespoons oil, and some salt and pepper to taste.
Sit the fish portions on top; drizzle with the remaining 2 tablespoons oil and season with salt and pepper.
Bake until the fish is opaque, firm to the touch, and just starting to flake, 12-15 minutes.
Remove from the oven and let stand briefly before serving with a garnish of chopped parsley.